The EGFR is a ubiquitously expressed 180 kD membrane tyrosine kinase that dimerizes upon binding EGF, transforming growth factor alpha, or other ligands. Dimerization initiates downstream signaling that elicits extensive phosphorylation of the receptor resulting in mitogenesis and protection against apoptotic stimuli. EGF receptor expression is amplified in many squamous carcinomas and in the bronchi of high-risk smokers. The receptor is internalized and degraded after ligand binding. EGFR extensively interacts with a number of proteins and is also reported to be a cellular receptor for cytomegalovirus. The Poly6213 antibody recognizes the human, mouse, and rat EGFR and has been shown to be useful for Western blotting.